Acoustic Measurement of RF Breakdown in High-Gradient RF
Structures

We are developing techniques for processing the high gradient (75MV/m),
X-band accelerating structures for the NLC. Accelerometers attached to the structures
detect surprisingly large acoustic signals, believed to be due to the RF heating. On
a pulse which causes breakdown, these signals increase substantially, producing up to
50 G acceleration at 20KHz. The timing and amplitude of these acoustic signals can
provide information on the location mechanism of the breakdowns.